FUEL CELL STACK

A fuel cell stack includes a cell stack in which a plurality of unit cells each including a pair of separators is stacked together. The fuel cell stack includes a seal sheet configured to seal between adjacent unit cells. The pair of separators each include a seal line rib on a seal sheet side of the separator, the seal line rib serving as a seal line with the seal sheet. Among two facing separators that are a first facing separator and a second facing separator facing each other while sandwiching the seal sheet between the adjacent unit cells, the first facing separator includes a protruding portion on at least one part of the seal line rib, and the second facing separator includes a recessed portion in the seal line rib that is configured to fit the protruding portion.